Describe how parts of human eye are adapted to their functions.

• The sclera/sclerotic layer is fibrous to maintain the shape of the eyeball;
• The cornea is curved to refract light onto the retina; It is transparent to allow light to enter the eye;
• The lens is biconvex to refract light onto the retina; It is transparent to allow light into the eye;
• The choroid is heavily pigmented to absorb stray light; It is also highly vasularised to nourish the eye;
• The aqueous humour which is transparent to allow light to pass; It is also rich in nutrients and oxygen to nourish the eye tissues;
• The vitreous humour is viscous to maintain the shape of the eyeball; It is also viscous to refract light; Transparent to allow light pass through;
• Ciliary body has suspensory ligaments which hold the lens in position;
• Has ciliary muscles that contract and relax to alter the curvature of the lens (during accommodation);
• Iris has an aperture called pupil which allows light enter the eye; Iris is also pigmented/has melanin to absorb light; give the eye its colour;
• Retina has photoreceptors / light-sensitive cells which perceive light of different intensities
• Retina has fovea centralis which is highly concentrated with cones to perceive light of high intensity;
• Rods are located in the peripheries of the retina to perceive light of low intensity;
• Has optic nerves which transmit light impulses to the brain;

Describe how parts of human eye are adapted to their functions.